It is well known to use voltage regulators in association with voltage and current sources to regulate the output of those sources before delivery to a load. One common application of voltage regulators is in motor vehicles. Typically, in this instance the voltage regulator is connected between a generator and a battery to ensure that the voltage delivered to the battery remains at a constant level. To keep the voltage at the desired level, the voltage regulator includes regulation circuitry, and often, over voltage protection circuitry. Some voltage regulators additionally include current limiting circuits which limit the current flow from the generator to the battery to assure that the battery is not subjected to excessive current levels. Current limiting is especially important in heavy-duty voltage regulators such as those used for construction equipment or by the military.
The current limiting circuits used in prior art voltage regulators limit the current to a predetermined maximum level which is chosen based on the needs of vehicle in which the voltage regulator will be employed. The current limit is set at a single point and the regulator thereafter limits the current at that predetermined level. While this procedure is satisfactory for regulators which are intended for use in a specific class of vehicles or applications, the voltage regulators are not interchangeable with regulators in other classes of vehicles or applications which often have different current requirements. Consequently, different regulators must be stocked for different needs.
It is desirable to have a voltage regulator which may be installed in a number of different vehicles by simply and easily selecting the appropriate current limit level prior to or even after installation. In military applications, where vehicles may have both a main generator and a back-up generator which provide current at different levels, it is desirable to provide a voltage regulator which can limit the current at a selected one of a plurality of current limits so that a single voltage regulator may be used in the vehicle, the required current limit being selectable by the vehicle operator or automatically.